In some applications, cooling fan drive systems installed on engines have been powered by a separate hydraulic pump. For engines including both a hydraulic system and a traditional fan drive system, multiple engine hydraulic pumps were a necessity. To make engines more compact and reliable, it is desirable to reduce the number of engine pumps. Additionally, it is desirable to control the fan drive system independent of engine speed to avoid wasting system energy. While traditional systems have performed magnificently for many years, there remains room for improvement in these areas.
The present invention is directed to overcoming one or more of the problems set forth above.